a. Field of the Invention
The instant disclosure relates to positioning and navigation of a medical device. More specifically, the instant disclosure relates to correction and scaling of a coordinate system for a positioning and navigation system.
b. Background Art
Various systems are known for determining the position and orientation (P&O) of a medical device in a human body, for example, for visualization and navigation purposes. One such system is known as an electrical field-based or impedance-based positioning system. Electrical field-based systems generally include one or more pairs of body surface electrodes (e.g., patches) outside a patient's body, a reference sensor (e.g., another patch) attached to the patient's body, and one or more sensors (e.g., electrodes) attached to the medical device. The patch electrode pairs can be adjacent, linearly arranged, or associated with respective axes of a coordinate system for such a positioning system. The system can determine P&O by applying a current across pairs of patch electrodes, measuring respective voltages induced at the device electrodes (i.e., with respect to the reference sensor), and then processing the measured voltages.
Because electrical field-based systems employ electrical current flow in the human body, the coordinate systems can be non-homogenous, anisotropic, and not orthonormal (i.e., the basic vectors of the coordinate system are not guaranteed to be at right angles to one another or to have proper unit lengths). As a result, geometries and representations that are rendered based on position measurements using such systems may appear distorted relative to actual images of subject regions of interest.